Allow me to translate for people over 10 years old ....
DME is FREE round-trip transportation between Orlando's airport (MCO) and your WDW resort. About 3 weeks before you leave you'll receive special DME luggage tags (sticky paper) to put on your checked luggage. Once you check it in at your home airport, you won't see your checked luggage again until it "magically appears" in your WDW resort room.
When you land at MCO, skip baggage claim -- remember, your bags will be delivered to your room (you put on those special luggage tags to tell employees behind the scenes at MCO to pull that luggage and ship it to Disney). Go directly to the DME Welcome Center and check in. They'll tell you which bus queue to get in. You'll ride a very comfy bus to your WDW resort -- there may be people on there from up to 3 other resorts, as well.
Probably 2-4 hours after you land, your luggage will "magically appear" in your resort room, whether you're there or not. Because it won't be there immediately, you need to pack essentials in your carry-on, in case the luggage is delayed by the airline or by DME. Don't screw yourself by HAVING to wait for your luggage and be frustrated that it's arriving late and you're getting a late start to your vacation.
On the day you return home, you also get a free ride back to MCO from your resort. Most people have to get their own luggage to the DME bus, and then handle it once back at MCO as well. Some people, those who are flying on the short list of "participating airlines," get their luggage handled for them just like on the in-bound trip, just in reverse (they check in their luggage at their resort and won't see it again until it's on their home airport's baggage claim carousel, plus they get to receive their actual airline boarding passes at their resort, which saves time at the airport later in the day).
The short version: DME is a FREE bus ride airport to WDW hotel, luggage delivered to your room, a free bus ride back to the airport, luggage may or may not be handled for you based on which airline you use.
-- Eric
